1. Field of the Invention
The present invention generally relates to a method for enhancing the marketable characteristics of a given product, and especially a perishable product, by exposing said product to one or more selected agents (e.g., a liquid, vapor, aerosol, or gas) in a predetermined, sequential order of delivery and exposure, while said product is maintained within a sealed, consumer-ready package. More specifically, the present invention relates to in situ method for processing a perishable product, where said method contemplates the employment of one or more chemical agents specifically selected for use with a given product, where said agent(s) are applied to the product while it is maintained within a sealed gas tight container, where further said agent(s) are employed at a selected concentration, temperature, pressure, and for a time sufficient to establish a predetermined modification of the particular product for retail presentation.
2. Description of the Prior Art
Perishable products, specifically meat, poultry, or fish products, are generally cleaned and packaged in bulk at a slaughter house or other processing facility preparatory to shipment to various retail outlets. These products are commonly packaged in containers such as plastic wrapped trays, pouches of plastic, paper or plastic coated paper bags, food storage tubes and the like. Upon reaching the retail outlet, the products are sorted, cut or otherwise handled for repackaging into containers that are typically pliant relative to rigid cans, bottles and cans in that they are flexible or soft to the touch. These containers are frequently transparent, as in the case of meats and poultry, to enable retail customers to view the product. Such products, especially meats, are commonly packaged in the ambient air atmosphere naturally occurring at such facilities.
Packaging of perishable products in such a fashion, however, ordinarily results in a fairly rapid reduction of the quality of the product as the product begins to age on the shelf with a resultant unacceptable appearance, smell and taste associated with bacterial chemical or biochemical deterioration. This phenomena occurs, though at a slower pace, even when such products are maintained in a refrigerated condition.
Product spoilage is partially a result of the multiplication of bacteria introduced onto the surface of the product during processing. Contamination of this sort is particularly pronounced in the processing of poultry. Moreover, the atmosphere introduced into the container of all perishable products also contributes to bacterial deterioration since such atmosphere contains a variety of airborne bacteria. Spoilage is also enhanced by "cross contamination" which is often brought about as a result of the common handling of products by human or mechanized devices during the packaging stage.
The rate and extent of lipid oxidation, color degradation, bacterial growth, texture changes and dehydration determines in large part the shelf life of the product. In this connection, a perishable product is generally considered to have a shelf life determined by the amount of time necessary for the deterioration to reach proportions which render the product unfit for consumption. This shelf life varies depending on the product and the conditions under which the product is processed and packaged. Fish and poultry traditionally have very short shelf lives when stored in an unfrozen state, whereas the shelf life for meat is generally somewhat longer. Regardless of the type of product, however, the presence of certain bacteria, especially pathogenic bacteria, can render the product dangerous for consumption even when present in small amounts. As a result of the above described problems relating to bacterial growth and other deteriorative changes, perishable products are generally refrigerated or frozen to enhance their shelf life.
A lowering in temperature is effective to retard the deterioration in the quality of the produce since lipid oxidation, color degradation, bacterial growth, and texture deterioration are slowed. For this reason, a perishable product generally will not spoil if frozen, but will almost immediately spoil if stored at room temperature in the absence of preservatives. However, even under frozen conditions, other quality properties other than microbiological deterioration may be sacrificed and thus render the product less usable after storage.
A number of techniques have evolved to utilize the benefits of freezing. One commercial preservation and storage method involves subjecting various products, especially fish and poultry, to temperatures slightly below 32.degree. F. (0.degree. C.). This technique, often referred to as "crusting" literally involves the freezing of the outer layer of the product. Products subjected to this technique are "slacked out" and displayed for sale in a refrigerated, non frozen state. Bulk retail and institutional packages of various perishable products are sometimes handled in this fashion.
Some products, however, especially poultry products, are felt to deteriorate in quality once subjected to freezing. Additionally, it is often times undesirable to freeze a product if further processing is contemplated at a secondary processing facility. For these reasons, other techniques have been developed to store or transport the product while maintaining the product at temperatures above freezing.
One such technique is vacuum packing. Vacuum packing inhibits bacterial growth by removing the operative oxygen environment necessary to sustain aerobic growth. Disadvantages with vacuum packing, however, include the purplish color induced in meat products which often times diminishes the appearance of such products for purposes of retail sale. Vacuum packing also results in the creation of an undesirable liquid exudate which is caused by package pressure differential. If commercial sale of vacuum packed products is desired, the product also must often be removed from the vacuum pack and exposed to oxygen so that the meat may "bloom." When exposed to oxygen, however, surface bacteria derived from the processing or packing operation, but keep in check during vacuum packaging, are then able to multiply and soon begin to move the product toward spoilage.
Other non-frozen techniques involves packing the product in a carbon dioxide atmosphere. A CO.sub.2 atmosphere, like the vacuum pack, also inhibits the growth of aerobic bacteria. Thus the product, when exposed to an aerobic environment, begins to rapidly degrade as a result of residual bacteria. Additionally, the product often absorbs the CO.sub.2, thus creating a negative pressure differential within the package and thereby making the package prone to collapse.
The above described techniques are useful, therefore, only from the standpoint of marginally prolonging the life of a perishable product during shipping, or when it is otherwise possible to maintain an aerobic environment around the product. Moreover, these techniques fail to inhibit the growth of anaerobic bacteria and do not maintain other desired quality characteristics important in retail sale.
Ozone (O.sub.3) has long been widely used as an oxidizing agent for bacterial, virus, and mold control for meat and fish storage, fresh fish processing, produce storage, restaurants, cooling towers, animal feed products, marine life, beverage containers, swimming pools, potable water systems, and tertiary waste systems. Ozone is also currently widely used for odor control in air conditioning systems, industrial processing operations, restaurants, mortuaries, rest homes and other applications. Ozone gas is a very strong oxidizing agent, having an oxidation potential more than twice that of chlorine and approximately three times that of hydrogen peroxide. Ozone also has the advantage of breaking down upon use as an oxidant into oxygen, which is normally beneficial. The use of ozone for the sterilization or preservation of food products is generally described in U.S. Pat. No. 4,549,477, which discloses both the historical applications (batch process) as well as the application of ozone in a continuous process whereby the perishable product is moved through a treatment zone filled with ozone.
Disadvantages associated with the techniques described in the '477 patent includes the possibility of recontamination of the product after it is moved out of the ozone flushed region and into a packaging area. This possibility of contamination is enhanced if the product is not already positioned in the package but must be positioned either mechanically or manually. Further, the aforedescribed processes do not allow for the possible retention of the activity of the agent to be maintained by confinement to the smaller space involved with a product in a retail package.